The invention relates to a method of preparing a disappearing model, and more particularly, to a method in which when the disappearing model of a complicated contour is prepared by dividing it into a plurality of disappearing model elements and bonding and fixing afterwards, the forcing out of an adhesive toward the inside of the elements can be prevented.
The invention further relates to a composite molding method using a metal and a synthetic resin and to a molding produced thereby. More particularly, it is directed to a method which allows a disappearing model to be prepared easily by utilizing a casting method with the disappearing model.
The invention still further relates to a method of preparing a disappearing model, and more particularly, to a method which allows a disappearing model having a complicated shape to be prepared easily without dividing it.
There is a casting method which involves the use of a disappearing model. The disappearing model is made, e.g., from a foam styrol and has the same contour as a product to be cast. Such a disappearing model is placed inside a molding box and is enclosed by molding sand, so that molten metal can be poured into the enclosed disappearing model. Accordingly, such disappearing model becomes fused and has disappeared to allow the molten metal to be poured into the lost portion. As a result, a product having the same shape as the disappearing model can be produced.
The following problems have been addressed when the thus constructed conventional disappearing model is to be fabricated. For example, let us consider a disappearing model 101 having a simple shape such as shogun in FIGS. 14 and 15. This model has a hollow portion 103 extending straight, and by using a slide core of a metal mold or the like, the disappearing model 101 having such hollow portion 103 can be prepared easily.
In contrast thereto, a disappearing model 105 such as shown in FIGS. 16 and 17, a hollow portion 107, having steps, cannot be produced using the simple method with the slide core of a metal mold or the like. Employed to overcome this problem is a method in which the disappearing model 105 is prepared in two pieces and the two are bonded together with an adhesive.
However, a key to this method using the adhesive is the amount of the adhesive to be used. For example, too large an amount of adhesive may sometimes cause the adhesive to be forced out of the bonding surfaces. A portion of the adhesive forced outside the disappearing model can be chipped off, however a portion of the adhesive pressed inside the disappearing model cannot be taken away easily, thus causing defects when a product is obtained while cast with such forced-out adhesive unremoved. Further, too few adhesive results in forming a gap between the bonding surfaces, causing graver product defects.
A method of preparing a disappearing model using a molded body made from sand such as shell or cold box process is also available. This method will be described with reference to FIGS. 18 through 26. As shown in FIG. 18, a molded body 109 made from sand such as a shell or cold box process shown in FIG. 19 is molded using a box 111 for forming the molded body. Then, as shown in FIGS. 20 and 21, both a disappearing model 119 made from a foam resin and the molded body 109 are integrated using a disappearing model 115 and the molded body 109 (see FIG. 21).
Then, as shown in FIG. 22, a runner with pouring gate 121 is bonded and fixed onto the body integrating the disappearing model 119 and the molded body 109. And as shown in FIG. 23, not only a facing by coating 123 is applied, but also the body with the facing by coating 123 is placed inside a molding box 127 that is filled with molding sand 125. Thereafter, molten metal is poured into the body enclosed by the molding sand to prepare a molding 129 shown in FIG. 25. Then, not only the runner with pouring gate 121 and a like portion which are unnecessary are removed, but also the molded body 109 is removed, so that a molding 131 such as shown in FIG. 26 can be obtained.
The method using the molded body 109 entails destruction of the molded body 109. Also, the specific weight of the molded body 109, being 1.4 to 1.6, is heavier than that of the disappearing model 119 (the specific weight of the disappearing model 119 is 0.020 to 0.025), thus imposing the problem that the molded body 109 is hard to handle and that the handling cost is high. Specifically, part of the disappearing model becomes broken. Further, as shown in FIG. 23, in the process of applying the facing by coating 123, the molded body 109 absorbs the moisture of such facing 123. As a result, it takes time to remove the moisture of such facing 123, and if the casting process is proceeded without satisfactorily removing the moistrue of such facing 123, grave casting defects are caused.
A method of fabricating a molded product such as an intake manifold includes casting if it is made from metal such as aluminum, and die forming if made from a synthetic resin. In casting, a method using a so-called disappearing model is available. More specifically, the disappearing model that is modeled upon the contour of a product is prepared and placed in sand, and molten model is then poured into the model. As a result, part of the disappearing model disappears with the molten metal introduced into the lost part, so that a product having a predetermined contour can be cast. Also, in die forming, an injection molding is available.
The following problems have been addressed with the above-mentioned conventional construction. For example, let us think about a case in which an intake manifold 401 such as shown in FIG. 27 was fabricated according to the conventional method. When made from metal such as aluminum, the advantages are that the molded product is strong and that thick portions 403 can be molded by the casting method with a disappearing model. However, the disadvantages are that it is hearty and that it is hard to prepare a thin portion 405 by the casting method using the disappearing model. The reason is that if the thin portion 405 is molded by preparing a foam molded body, surrounding the foam molded body with sand, and poring molten metal into the foam molded body, then the heat of the molten metal is dissipated into the sand, with the molten metal being solidified so quickly that casting defects are caused.
On the other hand, when the intake manifold is made from a synthetic resin, the advantages are that the product is light and that the thin portion 405 can be molded easily, but the disadvantages is that it is not so strong, with an additional problem of having to use expensive molds.